All 89 bee plants
Field poppy pollen
Papaver rhoeas
Very dark grey, nearly black, in the grey range.
FloweringJune to July
PollenGood
NectarNone
SeasonSummer
WhereFarmland, Waste and verge
Pollen only. The near black load is striking, and close to oriental poppy.

Easy to mistake for these
Closest pollen colours in our set, measured the same way the pollen identifier scores a match. Colour alone will not settle it, so check the flowering months and what is actually growing near your hives.
Confused with in the field
Noted by name in our own records, rather than worked out from the colour.
Out at about the same time
Saw a load like this going in?
Sample the colour against all 89 plants, then keep a forage record per hive.